R. White, and J. Huang. Proceedings of the 33rd International ACM SIGIR Conference on Research and Development in Information Retrieval, page 587--594. New York, NY, USA, ACM, (2010)
M. Welch, U. Schonfeld, D. He, and J. Cho. Proceedings of the fourth ACM international conference on Web search and data mining, page 327--336. New York, NY, USA, ACM, (2011)